JP2007518118A - Circuit and method for driving a light emitting display - Google Patents

Abstract

The present invention proposes a circuit for the element (3) of the light-emitting display. The element includes current control means (4), first and second switching means (12, 10), and light emitting means (8). In one embodiment, signal holding means (6) is provided. Furthermore, a light-emitting display having a plurality of elements (3) is proposed. Furthermore, a method for driving the element (3) and the light emitting display has been proposed, and a control signal used with the method is also proposed.

Description

  The present invention relates to a circuit for a light-emitting display element and a circuit for a light-emitting display having a plurality of elements. The invention also relates to a method for driving elements of a light emitting display and the signals used in the method.

  A light-emitting display that produces light using light-emitting elements through which current flows has a large number of light-emitting elements placed in a suitable arrangement. In such a situation, the light emitting element outputs a light beam depending on an electric current flowing through them. The term “beam” refers to the total radiated power of the light source. Hereinafter, the term “current” is used to represent “electric current”. In the case of a matrix arrangement having a plurality of light emitting elements, a black and white or multicolor image is represented by a plurality of pixels. In the case of a black and white image, the image is divided into individual grayscale values of pixels. In such a situation, the gray scale value is a different light flux value. Different luminous flux values are created by corresponding currents flowing through the light emitting elements. In the case of a multicolor light emitting display, a plurality of light emitting elements of different colors usually interact with each other. When additive color mixing of each pixel is used, it is possible to create a color different from the original color of the light emitting element. The light emitting element has, inter alia, a light emitting diode. The light emitting diode is made based on a semiconductor material (for example, silicon, germanium), but a light emitting diode (OLED (organic light emitting diode)) based on an organic material can also be used. A feature common to all of these light emitting diodes is that the output light flux depends on the current flowing through the light emitting element.

  In particular, in the case of organic light emitting diodes (OLEDs), current / voltage characteristics are highly dependent on aging and process parameters during manufacture.

  In organic light emitting diodes, light is produced by passing a direct current through the organic diode material. In this case, the organic light emitting diode is forward biased. It is known that the forward voltage of an OLED varies from pixel to pixel and increases with time. Similarly, it is known that the current that generates a particular luminous flux remains relatively stable for a long time.

  Therefore, when the control voltage is used for driving, it is necessary to consider aging with respect to the forward voltage of the OLED.

  In the case of a specific manufacturing method of an organic light emitting diode, the electro-optical properties of the individual light emitting elements are in principle the same over a specific area. In this context, the term “electro-optical characteristics” relates to current / voltage characteristics and the associated luminous flux. Appropriate control of the manufacturing method allows these regions to be formed in such a way that these regions of electro-optical properties, which are in principle the same, spread over the light-emitting elements arranged in rows and / or columns. To do. Therefore, the driving method may require correction values provided in the respective regions of electro-optical properties that are in principle the same.

  Another method for compensating for time-dependent electro-optic properties involves driving performed using a control current. For this purpose, each light-emitting diode, ie each organic light-emitting diode, has, for example, a first current control means connected upstream thereof. The first current control means is connected to the second current control means in such a way that a current mirror circuit is obtained. In the case of a current mirror circuit, the second current control means has a reference current that flows through the second current control means when the corresponding control signal is at the control electrode of the second current control means. This control signal is supplied to the control electrode of the first current control means. In the case where the first and second current control means have the same characteristics in principle, the current flowing through the first current control means corresponds to the current flowing through the second current control means. The same characteristics of the two current control means compensate for thermal, manufacturing related and aging related changes.

In other embodiments of the current mirror, the mirror current can be applied at a specific ratio relative to the reference current. This embodiment of the current mirror will be described with reference to FIG. FIG. 4 shows the current control means 2 having the reference current i _ref flowing through the second current control means. The control electrode of the current control means 2 is connected to the control electrode of the further current control means 4, 4 ', 4 ". The mirror current flowing through the further current control means 4, 4', 4" is shown in the figure. in reference numeral i _m, i _{m ', "it} is represented by. additional current control means 4,4 i m', 4" when are the same, the current flowing through them, as well at the same is there. If the current control means 2 is the same for the further current control means, all currents are the same. At this time, a desired current can be set by applying a mirror current.

In a further embodiment of a current mirror, the current characteristic of the control means 2 and the current control means 4, 4 ', 4 "characteristics of the current _{i ref, i m, i m} ' and _{i m"} is each to each other specific ratios Selected to be.

  The use of a suitable current mirror allows the current required for control and the current flowing through the light emitting element to be selected independently of each other. In this way, as an example, the current required for control can be increased while the current flowing through the light emitting element is in an advantageous range. Furthermore, this is set individually so that the regions with different electro-optical properties remain limited in the required range of the control current and nevertheless all elements can be driven completely. Make it possible.

  In the case of a light emitting display for rendering a wide range of images, for example in a television receiver, the images are made in a non-interlaced or interlaced format. Non-interlaced or interlaced images are also called “frames” and “fields”, respectively. In this case, the image area is divided into rows and / or columns virtually and / or physically. In the case of image rendering using interlaced images, as an example, a partial image having only even or odd rows of all images is rendered first. Next, another interlaced image is rendered. In the case of non-interlaced images, all images are set up. Interlaced rendering is also referred to as “interlaced scanning” and non-interlaced rendering is also referred to as “sequential scanning”. When rendering a moving image, the non-interlaced or interlaced display is also replaced at regular intervals by each other image with altered image content to produce a resulting fluid motion signature. In this case, the frame frequency depends on, for example, each television standard.

In today's light emitting displays having light emitting elements arranged in a matrix arrangement and having individual current control means, the individual light emitting elements are driven continuously in rows or columns. A light emitting element for such driving is shown in FIG. The current control means 4 is connected in series with the light emitting element 8 between the operating voltage VDD and the ground. The control signal is supplied to the control input of the current control means 4 through the switch 12. In this case, the control signal is the control voltage U _Set . In this example, the switch 12 is controlled such that only a single light emitting element in the array of light emitting elements is driven. In the drive scheme required for this circuit, the time period during which the light emitting diode emits light is relatively short. Depending on how many light emitting elements are present in the array of light emitting displays, the active time period is reduced. Since the human eye is a natural system with a low-pass filter response, it is possible to compensate for short periods of activity by appropriately increasing the luminous flux during the period of activity.

  It is also conceivable that each current control means has a light emitting display that is permanently activated by a control signal. In that case, the switch 12 can be deleted. However, the very large number of control lines required reduces the area available to represent light on the screen.

In the case of the light emitting element shown in FIG. 2, a signal holding means 6 is added to the circuit between the control electrode of the current control means 4 and the operating voltage VDD. The control signal U _Set applied when the switch 12 is closed is kept constant by the signal holding means 6 until a new control signal U _Set is applied when the switch is opened. This makes it possible to extend the active time period during which the light emitting element 8 emits light. At this time, the active time period extends over almost the entire period during which the image is set up. This reduces the required luminous flux to be emitted during the active time period. The observer's eyes can then combine less light over a longer time period, so that the same amount of light is captured and the same image trace described with reference to FIG. 1 is obtained. .

FIG. 3 shows the elements of a light emitting display as shown in FIG. The element is marked by a dashed frame 1. In this example, the control signal S is drawn from the control electrode of the current control means 2. When the switch 12 is closed, the current control means 2 forms a current mirror circuit with the current control means 4 of the element 1. In a light emitting display having a plurality of elements 1 in a grid arrangement, each element 1 is supplied with individual control signals depending on the image content. For this purpose, each control current i _prog is passed through the current control means 2. A control current not shown in FIG. 3 continuously activates the switches 12 of the various elements 1 of the light emitting display.

  It is desirable to simplify the driving of a light emitting display having a light emitting element of the above type. It is also desirable to identify improved control signals that drive the light emitting elements. Finally, it is desirable to demonstrate an improved method for driving a light emitting device.

  In order to achieve this object, the element of the light-emitting display according to the invention has current control means connected in series with the light-emitting means. The control line coupled to the current control means has first and second switching means arranged in series. In a further embodiment, the current control means further comprises the signal holding means. When the first and second switching means are closed, the control signal according to the invention is applied to the current control means. In the case of elements arranged in a grid having columns and rows, one switching means selects a row and one switching means selects a column in which the elements are arranged. The current control means controls the current flowing through the light emitting means. The light emitting means emits a light beam depending on the current. When the luminous flux reaches the desired size, one of the two switching means is opened. In the case of row actuation, the switching means for selecting a column is first opened. In the case of column actuation it is therefore its switching means to select the column.

  The control signal used has a continuously increasing graph, for example a lamp shape. Between the two periods of driving, there can be an idle period in which the control signal is essentially unchanged.

  The present invention will be described in further detail below with reference to the accompanying drawings.

  In the drawings, the same or similar components or elements are denoted by the same reference numerals. 1 to 4 have already been described in the background art of this specification. Accordingly, they will not be described in further detail below.

FIG. 5 shows the inventive element of a light-emitting display as a circuit diagram. One connection part of the current control means 4 is connected to the operating voltage VDD. The other connection portion of the current control means 4 is connected to the first connection portion of the light emitting means 8. The second connection portion of the light emitting means 8 is connected to the ground node. The current control means 4 is a transistor, for example. In the present embodiment, the light emitting means 8 is a light emitting diode, but the present invention is not limited to the use of the light emitting diode. The control electrode of the current control unit 4 is connected to the first control signal U _ramp via the first switching unit 12 and the second switching unit 10. The control signal U _ramp is, for example, a control voltage as used in the method of the present invention. The dashed frame 3 indicates that the above components form the elements of a light emitting display according to the present invention.

Hereinafter, the method of the present invention for cyclically driving the light emitting display element 3 shown in FIG. 5 will be described. The element 3 is a part of a light-emitting display having a plurality of elements 3 arranged in rows and columns as an example. Initially, the two switching means 10, 12 in the element 3 are closed. As an example, the first switching means 12 is used for selecting a column, and the second switching means 10 is used for selecting a row in which the elements 3 are arranged. Replacing the arrangement of the switching means 10, 12 is not important to the present invention. At this time, the control signal U _ramp is applied to all the second switching means 10. It reaches the control electrodes of the first current control means 4 when both the first and second switching means 12, 10 connected to the control electrodes of the first control means 4 are closed. At a specific time, the light beam emitted by the light emitting element 8 reaches a desired size. At this time, one of the switching means is opened. If the rows of the light emitting display are driven continuously, the first switching means 12 for selecting the columns is first opened. The control signal U _ramp continues to increase further continuously until it reaches a predetermined final value. The first switching means 12 in the other elements 3 of the currently driven row are likewise opened at each particular time. The driving cycle of the current row is terminated when the control signal U _ramp reaches its predetermined final value. All the second means 10 coupled to the current row are now opened and the method of the invention is repeated for the next row. When all rows are driven, driving begins again with the first row. If the drive sequence is performed in a row, the order in which the switching means are opened should be changed accordingly.

  The above method only results in the emission of light at the respective light emitting element 8 of the element 3 until one of the two switching means 10, 12 is opened. In order to produce a suitable image trace in the case of a two-dimensional light emitting display, the luminous flux emitted by each element 3 at a specific time needs to correspond to the desired luminance value of the image. Since driving only causes light emission during part of the driving cycle of the entire light emitting display, the luminous flux needs to be correspondingly larger in a short time. The integration of the light quantity to give a two-dimensional image trace is performed in the observer's eyes as already mentioned above. However, the parallel operation of elements arranged in rows or columns advantageously extends the effective light emission time of the elements and reduces the maximum required drive current compared to the sequential driving of each individual element in the row. .

FIG. 6 shows a further embodiment of a light emitting display element according to the invention. The circuit shown in FIG. 6 largely corresponds to the circuit shown in FIG. Further, the signal holding means 6 is disposed between the control electrode of the first current control means 4 and the operating voltage VDD. When one or both switching means 12, 10 are opened, the signal holding means 6 holds the control signal U _ramp until both switching means are closed again and a new control signal is applied. As an example, the signal holding means 6 is a capacitor that holds a control voltage until a new control voltage is applied. Under such circumstances, the time period during which light is emitted may advantageously be further increased compared to the circuit of FIG.

  The driving method described with respect to the circuit of FIG. 5 is similarly used for the circuit of FIG. In the case of the method to be used here, in principle only the time when the first switching means 12 is opened needs to be changed. The signal holding means 6 holds the flow of current through the light emitting means 8 until a new period applies a new control signal to the control electrode of each first current control means 4, so that each current is smaller. Can be. The integration of the luminous flux that occurs in the observer's eye can integrate the smaller luminous flux due to the smaller current over a longer period of time, and as a result, the same amount of light is captured and the same image trace is produced. Brought about.

  Needless to say, a color image can be rendered by using the three primary colors red, green and blue for additive color mixing. Other color combinations are considered according to the desired impression. In either case, the corresponding group of elements 3 of the pixels needs to be driven so that the desired color is created for each pixel as a result of the color mixture. The methods described above with respect to FIGS. 5 and 6 can be used as well.

FIG. 7 shows an element of a light-emitting display according to the present invention. The components of the element in the frame 3 indicated by the broken line basically correspond to the components of FIG. In the case of the embodiment of the inventive element of the light emitting display shown in FIG. 7, the control signal is derived from the control electrode of the second current control means 2. The second current control means 2 is formed of a transistor, for example, a field effect transistor (TFT) in the drawing. When the first and second switching means 12 and 10 are closed, the first and second current control means 4 and 2 form a current mirror circuit. In this case, the current i _ramp passed through the second current control means 2 represents an operation signal. The applied current i _ramp is generated at the control electrode of the second current control means 2 and applied as a control signal to the control electrode of the first current control means 4 via the first and second switching means 12 and 10. Control potential. The applied current i _ramp may be used as an operation signal in a circuit that does not involve the signal holding means 6. In that case, the switching times of the switching means 10 and 12 need to be adapted accordingly.

The second current control means 2 is shown in FIG. 7 as having a single transistor. In order to set a specific ratio of the applied current i _ramp to the mirror current i _OLED , the second current control means 2 can be composed of a plurality of transistors connected in parallel. This is particularly advantageous when the second current control means 2 operates a plurality of first current control means 4. In one preferred embodiment, the transistors have the same characteristics. FIG. 8 shows this embodiment as an example. Element 3 corresponds to element 3 in FIG. The current control means 2 surrounded by the broken line frame is formed by a plurality of interconnected transistors 21, 22, 23 in this example. In addition to element 3, element 3 ′ is shown. The element 3 ′ is supplied with the control signal S in parallel with the element 3. In FIG. 8, the components of the element 3 ′ correspond in principle to the respective components of the element 3 and are represented by the same reference numerals. If components with different characteristics are used, this can be compensated, for example, by a suitable adaptation of the current control means.

FIG. 9 shows a further embodiment of a light emitting display element. When the individual elements 3 are arranged in rows and columns, the first current control means of the plurality of elements arranged in the rows and / or columns are collectively used as the common second current control means 2. Connected to. A third switching means 13 is provided and connects the second current control means 2 in a state where it can be switched to the actuation signal i _ramp . Preferably, only one second current control means 2 is absolutely connected to the activation signal i _ramp at any time. In that case, as an example, the driving method includes a step in which a row is first selected, and a step in which a group of elements 3 in the selected row is subsequently operated.

If the first and second switching means are driven appropriately, it is also possible to place the signal holding means directly in a specific state when the third switching means 13 is opened. Thus, for example, the control signal U _ramp can be reset for individual or multiple elements. As an example, in that case, the reset is performed using a reverse diode in one of the field effect transistors used as the second current control means 2.

In another embodiment of the element 3 of the present invention, the fourth switching means holds the signal as a reset means so that the control signals U _ramp , S held in the signal holding means 6 can be reset in a predetermined format. Coupled to means 6. Alternatively, this further switching means (not shown) may be coupled to the control connection of the second current control means 2. In this case, the signal holding means 6 in one or more elements 3 are advantageously used with a single signal reset means by switching the corresponding first and second switching means of the elements 3 in an appropriate order. Can be reset to As an example, the reset unit may discharge the electric charge accumulated in the capacitor that operates as the signal holding unit 6 to the ground or the operating voltage VDD.

  FIG. 10 shows a specific embodiment of the circuit of FIG. In such a situation, the first and second switching means 12 and 10 are provided by transistors 16 and 14. The control electrodes of the transistors are supplied with respective signals Sel1_1 and Sel1_2.

FIG. 11a shows an exemplary characteristic diagram for one period of a control signal for use in a light emitting display element according to the invention and the method of the invention. The figure shows a current i _prog that increases continuously over time from the starting value at t0, or a voltage u _prog that increases continuously from the starting value. The ordinate in FIG. 11a is the time axis. The constant increase of the control signal ends at time t1. At time t1, a new driving cycle of the elements of the light emitting display starts. The curve shape of the control signal does not necessarily correspond to the sawtooth shape shown in the figure. In this situation, any signal that constantly increases can be considered, for example, an exponential or logarithmic increase. Furthermore, it is not absolutely necessary to have a cycle start immediately after the end of the cycle. Similarly, there may be idle time between the end of a cycle and the start of a new cycle. In this case, the idle time may be at either the start or end of the cycle. If there is an idle time at the start of the cycle, the output signal is retained, otherwise the respective set signal is retained.

  The control signal of the present invention can be generated using, as an example, an appropriately controlled digital / analog converter or an appropriately controlled pulse width or pulse density modulator. For this purpose, the control circuit generates pulses having a specific length and a constant frequency, or pulses having a constant length and a variable frequency. Such pulses are combined to form a control signal. In the case of generation by pulse width or pulse density modulation, the pulse control signal needs to be smoothed with an appropriate filter. Alternatively, in the case of the sawtooth shape, the control signal can be generated using an analog circuit using, for example, a constant current source for charging the capacitor and a switch for discharging the capacitor at the end of the cycle. . In this case, the digital / analog converter is not required to operate, but rather is required to switch the row in which the signal is applied to the first and second switching means 12 and 10. As an example of the development of the circuit, an analog / digital converter is provided, which samples the control signal and transmits each sampled signal to the control circuit. The control circuit uses the sampled instantaneous value to generate the control signals for the first and second switching means. In this way, it is advantageously possible to compensate for unwanted fluctuations during signal generation.

FIG. 11b shows an exemplary graph of the control signal at the control electrode of the first current control means. The control signal follows the control signal graph of FIG. 11 a based on the closed first and second switching means 12 and 10. At time t2, one of the first or second switching means 12 or 10 opens and the signal holding means 6 is the magnitude of the control signal at this time u / i ₁ at the control electrode of the first current control means. Keep the thickness constant. At the end of the elapsed period at t1 and at the start of a new period thereafter, all the switching means 12 and 10 are closed again and the control signal again increases continuously from the initial value. If there is an idle time between two cycles, all current control means are, for example, placed in a predetermined state during this time. In one variation of the driving method, the idle time is relatively long relative to the cycle time. In this case, the elements of the light emitting display are set in a short time. For most of the idle time at the end of the operation cycle, the signal holding means of the element holds the set light flux. Only at the end of the idle time and before the start of a new drive cycle, the element is placed in a predetermined initial state. A longer time period with no change with respect to the set time allows a more stable image trail to be achieved. To enhance understanding, the above diagram does not represent any transient behavior that may occur in an actual circuit.

FIG. 12 shows a part of a light-emitting display having a plurality of elements 3 of the invention. In the figure, the element 3 has first current control means 104, 204, 304. The currents i _OLED1 , i _OLED2 and i _OLED3 flowing from the supply voltage VDD through the current control means 104, 204 and 304 flow to the ground through the light emitting elements 108, 208 and 308. The control electrodes of the current control means 104, 204, 304 have signal holding means 106, 206, 306 connected to them. The control signal S is supplied to the control electrode of the first current control means 104, 204, 304 via the first and second switching means 114, 116, 214, 216 and 314, 316, respectively. The first and second switching means of the element 3 are controlled by switching signals Sel1 to Sel6. Each element 3 is represented by a dashed frame. The control signal S is taken out from the control electrode of the second current control means 102. When the switching means 114, 116, 214, 216, 314, 316 are closed, the second current control means 102 switches each current mirror circuit together with the respective first current control means 104, 204, 304 of the element 3. Form. In this case, the control signal S is generated by the control current i _{ramp that} is supplied to the second current control means 102.

FIG. 13 shows a plurality of inventive elements of a light emitting display in a matrix arrangement for rendering a color image. Overall, six inventive elements 3 are shown in FIG. Each element 3 is surrounded by a dashed frame. Each element 3 corresponds in principle to the element of FIG. In this example, three elements 3 are provided for one pixel for the purpose of rendering a color image, one element 3 for each of the red, green and blue primary colors. Is provided. FIG. 13 shows two pixels having three respective elements 3. The control signal S is applied to the control input of the second current control unit 402. The control signal is generated by the applied current i _ramp that flows through the second current control means 402. Each of the elements 3 includes first and second switching means 416, 414, 516, 514, 616, 614, 716, 714, 816, 814 and 916, 914. The first and second switching means closed first in the element 3 are the control electrodes of the first current control means 404, 504, 604, 704, 804 and 904 of the element 3 in the respective current mirror circuit arrangements. Connect to the second current control means 402. The two pixels formed by the three respective pixels are, as an example, placed in a row of light emitting displays formed from a plurality of pixels arranged in rows and columns. The control input Line is used for simultaneously controlling the first switching means 416, 516, 616, 716, 816 and 916 of the element 3, respectively. The respective second switching means 414, 514, 614, 714, 814 and 914 of the element 3 are controlled by individual switching signals Sel1_R, Sel1_G, Sel1_B, Sel2_R, Sel2_G and Sel2_B.

  In the development of the circuit of FIG. 13, the current control means for each color is in such a way that light-emitting means of different sensitivities are considered for each color. Thus, a single control signal S may be used to operate each light emitting means for various colors in an optimal manner. In this case, one possible implementation of such a development uses the characteristics of the current mirror circuit shown in FIG. In this case, each light-emitting means relating to various colors is assigned a current control means for reproducing the reference current by weighting with each specific coefficient.

  FIG. 14 shows a plurality of elements 1 of a light emitting display arranged in rows and columns. Element 1 corresponds to the element known from the prior art shown in FIGS. The control signal S according to the invention is supplied to all elements 1 simultaneously. Each of the elements is also connected to an individual switching signal Sel1 to Sel15.

  The inventive method for operating this light-emitting display is in principle based on the method described in FIG. The constantly increasing control signal S is supplied simultaneously to all the elements 1 of the light emitting display. Each of the elements 1 corresponds, for example, to the element 1 of FIG. Each switching means 12 in the element 1 is initially closed. Next, the cycle of the control signal S of the present invention is started. At a particular time, the respective switching means 12 in the individual elements 1 are opened so that all of the elements 1 render the desired image. In such a situation, a new operating cycle is started after driving a complete image rather than after driving a row or column.

  It is also conceivable that the element 1 does not have any signal holding means 6. In that case, the method for operation corresponds in principle to the above method. The only difference is when each switching means is opened.

  The method described above with reference to FIG. 14 is particularly suitable when the light emitting display has fewer pixels or elements. In this case, it is advantageous to dispense with special column and row actuation. However, the method and circuit are not limited to small light emitting displays.

  FIG. 15 shows a part of a publishing display having elements 3 of the present invention arranged in rows and columns. The element 3 has the control signal S of the present invention supplied to them simultaneously. Furthermore, the switching signals Line1, Line2, and Line3 are simultaneously supplied to the elements 3 arranged in the row, respectively. Similarly, the elements 3 arranged in the column are simultaneously supplied with switching signals Col1 to Col5, respectively. Thus, a suitable combination of switching signals for rows and columns can be used to drive each element 3 individually.

  This light-emitting display requires the use of an operating method as described in FIG. At the start of the driving cycle, all switching means of the elements 3 arranged in the row or column are closed. Initially, the individual elements are driven together in each row or column by the control signal S until the individual switching means 10, 12 of the element 3 interrupt the connection to the control signal S in the appropriate column or row. . It is therefore possible to drive all the elements 3 of the light emitting display individually. In order to carry out a preferred variant of the method, the rows of the light-emitting display are initially selected with the appropriate switching signals Line1, Line2, Line3. Next, all columns are selected using the appropriate switching signals Col1 to Col5. Next, the control signal S of the present invention is applied to all the elements 3. However, it only reaches the control electrodes of those first current control means 4 arranged on the elements in the selected row. Whenever a particular desired signal value is achieved, the column switching signal breaks the connection between the control signal S and the individual elements 3. The control signal S continues to increase until it reaches a predetermined final value. Next, the operation cycle of the selected row ends. A new row is selected and the method is executed from the beginning. If all the rows of the light-emitting display are activated continuously, the operation starts again from the beginning in the first row.

FIG. 16 shows a part of a development example of the light emitting display of FIG. In the issuing display of the present invention, each of the plurality of elements 3-1, 3-2, 3-3 and 3-4 is integrated in a group. The elements correspond, for example, to the elements described with respect to FIG. Each group comprises a respective second current control means 2-1, 2-2, coupled to it in a switchable manner via switching means 13-1, 13-2, 13-3 and 13-4. 2-3 and 2-4. The switching means are supplied with respective row control signals Line n or Line n + 1 which are also supplied to the corresponding switching means of the elements 3-1, 3-2, 3-3 and 3-4. In the embodiment, adjacent groups with group indices -1 and -2 are connected to the same row control signal Line n. Adjacent groups with group indices -3 and -4 are connected to row control signal Line n + 1. The vertically arranged groups with group indices 3-1 and 3-3 and 3-2 and 3-4 are connected to the drive signals i _ramp1 and i _ramp2 . Furthermore, each of the elements 3-1, 3-2, 3-3 and 3-4 also has a column control signal Col m to Col m + 5 and a control signal S-1, S-2, S-3 or S-. 4 is supplied.

In the case of driving in a line-by-line format, a row is first selected using a row control signal Line. This closes the switching means 13 for each row. Corresponding switching means for row selection of elements 3 arranged in the selected row are closed as well. Thereafter, the switching means for selecting the column of the elements 3 is also closed. In the selected row, all elements 3 are now connected to respective control signals S that are applied to the control electrodes of the respective current control means 2. The drive signals i _ramp1 , i _ramp2 applied to the corresponding conductors are sent via the closed switching means 13 to their second current control means connected to the conductors. This _ensures that each drive signal i _ramp1 , i _ramp2 is applied only to one respective group of elements 3. The switching separation of the further elements and associated connection conductors reduces the capacitive load of the drive signals i _ramp1 , i _ramp2 . In the case of very small drive signals, capacitive loads can result in signal attenuation. The drive signals i _ramp1 and i _ramp2 each result in a constantly increasing control signal S. When the desired luminous flux is achieved for each element 3, the column control signals Col m to Col m + 5 open the corresponding switching means of the element 3. When a predetermined final value of the drive signals i _ramp1 , i _ramp2 is achieved, a new drive cycle starts, for example, in the next row in the case of parallel drive of rows.

  The number of elements combined in the group is not fixed at 3. In principle, any number of elements can be integrated into a group. It is therefore possible for each element 3 to be assigned to an individual second current control means 2, i.e. to form a group with only one element. In this case, the number of control conductors inevitably increases, but a greater degree of freedom is obtained for driving the individual elements.

It is also possible to create only the drive signal i _ramp1 and apply it to the conductor according to the second actuation signal i _ramp2 , for example via a multiplexer. In that case, by way of example, the groups are driven sequentially in rows rather than simultaneously in rows.

FIG. 17 shows details of further elements of a light emitting display according to the present invention. As described above with respect to FIG. 16, each of the plurality of elements 3-1, 3-2, 3-3 and 3-4 is integrated into a group having group indices −1, −2, −3 and −4. The The group of elements has respective associated second current control means 2-1, 2-2, 2-3 and 2-4. The elements 3-1, 3-2, 3-3 and 3-4 in the group also have control signals S-1, S-2, S-3 and S-4 and row control signals Line n and Line n + 1. And Col m + 1 is supplied from the column control signal Col m. The second current control means is connected in a switchable _manner to the conductor related to the drive signal i _ramp1 through the respective switching means 13-1, 13-2, _13-3 , and 13-4. In this case, the switching means 13-1, 13-2, 13-3 and 13-4 are supplied with individual switching signals G-1 to G-4. Therefore, in the case of groups arranged in rows and columns, any group can be selected individually. This means that a single drive signal i _ramp1 can be supplied to all groups individually.

  With the appropriate switching of the individual switching means in FIG. 3, the embodiment of FIG. 17 allows the signal S stored in the signal holding means 6 of the element to be deleted independently of the row selection.

  Also in this embodiment, the number of elements 3 in the group is not fixed at 3. It can assume any suitable value.

Furthermore, a plurality of drive signals i _ramp1 , i _ramp2 may also be used in this embodiment as described with respect to FIG. This provides an additional degree of freedom with respect to driving.

  In the preferred embodiment of the light emitting display of FIGS. 16 and 17, the respective sub-pixels (coupled to the pixels) for the primary colors of red, green and blue are combined in groups to render the colors.

  When a plurality of elements driven in a group use the second current control means, it is possible to use an interconnection of a plurality of current control means as shown in FIG. However, it is also conceivable that the interconnected current control means 21, 22, 23 shown in FIG. 8 are directly coupled to the respective elements 3. The physically close coupling further improves the desired tight coupling of the electrical characteristics of the first and second current control means.

  The elements in the light emitting display, the circuits described above for the light emitting display and related methods, and variations thereof, are not merely suitable for sequentially operating rows or columns. Interline scanning methods may also be used for operation. This advantageously provides compatibility with existing standards for image transmission without buffering of image sections. Further specific drive patterns are conceivable, for example by means of a row that operates simultaneously from both ends to the center.

  The embodiment of the current control means in the circuit described above with reference to the drawings is designed using p-channel field effect transistors. Alternatively, the circuit can be designed with n-channel field effect transistors. The arrangement of the control signal and the signal holding means and the light emitting means then has to be adapted accordingly.

  The use of field effect transistors for the current control means is advantageous when the signal holding means 6 is, for example, a capacitor. When such a signal holding means 6 is not provided, it is also possible to use a bipolar transistor.

  In the above embodiment, the transistor is used for the switching means. In either case, the bipolar transistor and the field effect transistor may be used for switching. However, the circuit of the present invention is not limited to a transistor as a switch. It is also conceivable to use mechanical, micromechanical, magnetic or optical switches.

  In principle, the circuit and method are suitable for any light emitting means that can have a light flux that is clearly controlled by the current. The present invention is not limited to the OLEDs or light emitting diodes (LEDs) listed in the description of the examples.

  The idle time between the two drive cycles described above with respect to one method variant is not limited to this variant. An idle time between two cycles can be provided for all of the above methods.

  The fourth switching means as the reset means described above with respect to the embodiment of the element 3 and the corresponding control are advantageously used in all embodiments together with the signal holding means 6.

1 shows a circuit for a light-emitting display element known from the prior art. Fig. 4 shows a further known circuit for a light emitting display element. Figure 3 shows a third known circuit for a light emitting display element. 1 shows a current mirror circuit known from the prior art. 1 shows a first embodiment of the circuit of the present invention for a light emitting display element. 2 shows a second embodiment of the inventive element of a light-emitting display. 3 shows a third embodiment of the inventive element of a light-emitting display. The modification of the current mirror circuit which has the element of the light emission display of this invention is shown. The development example of the light emitting display of this invention is shown. 8 shows a specific embodiment of the device of the present invention shown in FIG. Fig. 4 shows a control signal used with the method of the present invention. Fig. 11b shows the control signal of Fig. 11a in a particular operating state. Fig. 3 shows a plurality of elements of a light emitting display of the present invention arranged in a row. Fig. 3 shows a plurality of inventive elements of a light emitting display in a matrix arrangement for rendering a color image. Figure 2 shows a schematic diagram of the rows and columns of one embodiment of a light emitting display element for control according to the method of the present invention. Figure 2 shows a schematic diagram of the row and column arrangement of one embodiment of the inventive element of a light emitting display. Fig. 2 shows a partial view of a light emitting display according to the present invention. The fragmentary figure of the modification of the light emission display of this invention is shown.

Claims (16)

A light emitting means for emitting light when a current flows, a first current control means connected in series to the light emitting means and for supplying a control signal to a control electrode of the first current control means; and a first switching An element of a light-emitting display controlled by a signal and having a first switching means arranged when supplying power to the control electrode,
The second switching means controlled by the second switching signal is arranged in series with the first switching means when supplying power to the control electrode of the first current control means.
An element characterized by that.   The control electrode of the second current control means is connected in a switchable manner to the control electrode of the first current control means via the first and second switching means. 1. The element according to 1.   3. An element according to claim 2, wherein the first and second current control means form a current mirror circuit.   4. The element according to claim 2, wherein the drive signal is supplied in a switchable state to the second current control means via a third switching means.   The signal holding means is configured to hold the control signal when the first and / or second switching means interrupts the supply of the control signal to the control electrode of the first current control means. The element according to claim 1, wherein the element is connected to a control electrode of the first current control unit.   6. The element according to claim 5, wherein the control signal and / or the signal held by the signal holding means can be placed in a predetermined state by a fourth switching means.   7. A light-emitting display, characterized in that the elements according to claim 1 are arranged in rows and / or columns.   The light-emitting display according to claim 7, wherein the control signal is simultaneously supplied to a plurality of elements arranged in rows and / or columns.   9. The light-emitting display according to claim 8, wherein the common first switching signal is supplied to a plurality of first switching means included in elements arranged in rows and / or columns. A method of operating a light emitting display device according to claim 1, comprising:
Closing the first switching means at the start of a cycle;
Applying to the first current control means a control signal that continuously increases from a predetermined starting value;
When the luminous flux emitted by the light emitting means reaches a desired size, opening the first switching means;
When the applied control signal reaches a predetermined final value, starting a new period;
A method characterized by comprising: When the element of the light emitting display has second switching means connected in series to the first switching means,
Closing the second switching means before or after closing the first switching means;
Opening the second switching means before a new cycle is started;
The method of claim 10, comprising:   12. A method according to claim 11, wherein the first and second switching means are used to select elements from a very large number of elements arranged in columns or rows. A plurality of light emitting elements arranged in columns or rows operate simultaneously,
The columns or rows operate sequentially,
13. A method according to claim 11 or 12, characterized in that   The application of the first control signal continuously increasing from the start value is an application of current to the second current control means connected in a switchable state to the first current control means. 14. A method according to any one of claims 10 to 13.   15. The fourth switching signal is temporarily applied to a fourth switching unit that sets a signal held in the signal holding unit to a predetermined state. The method described in the paragraph.   16. A method according to any one of claims 10 to 15, wherein the idle time is provided between two periods.

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